Sabre-toothed cats, one-tonne bears and sloths the size of elephants all happily coexisted with humans for up to 3,000 years, but were extinct within 300 years after the climate of South America rapidly warmed.

Key points megafauna

Key points:

DNA in ancient bones shows South America's giant land animals died out 12,300 years ago

This is up to 3,000 years after humans settled

The disappearance coincides with rapid warming of climate

This may have changed vegetation and boosted human hunting

These new findings counter the "Blitzkreig" theory that humans simply hunted into extinction the world's biggest beasts, or "megafauna".

Instead the scientists suggested climate change was the trigger for the ancient giants' demise.

The research was led by Professor Alan Cooper at the University of Adelaide and is published today in the journal Science Advances.

He and his colleagues studied ancient DNA from carbon-dated bones and teeth found in caves across southern South America, to trace the genetic history of the populations.

They found that the megafauna all disappeared within a narrow 300-year time frame around 12,300 years ago.

Yet the fossil record showed humans had been at Monte Verde, on the edge of Patagonia, from about 14,600 years ago.

The team, which also included researchers from Chile, the US and the University of New South Wales, discovered the extinction of the megafauna coincided with a rapid warming of South America's climate.

"The conventional way of thinking [about megafauna extinction] is that humans moved through North America in a Blitzkreig way, where rapid exposure to hunting and populations of humans running around all over the place killed off everything, in this front overkill," said Professor Cooper.

"But the data from South America is strong evidence that that didn't happen.

"We've got a very long period of overlap — at least 1,000 years and probably 3,000 years — where nothing happens.

"You've got humans, you've got megafauna and nothing is going on, which is kind of a revelation.

"The point at which megafauna do go extinct 12,300 years ago is right when the climate starts warming rapidly after a prolonged cold period."

The only large species to survive the extinction event were the ancestors of today's llama and alpaca — the guanaco — and even these species very nearly died out.

Luck of the draw – the larger ancestors of these guanacos in Patagonia were one of only two large ice age herbivores that survived the extinction.